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IC 



9104 



Bureau of Mines Information Circular/1986 




Tin Reconnaissance of the Kanuti 
and Hodzana Rivers Uplands, 
Central Alaska 

By James C. Barker and Jeffrey Y. Foley 



UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 9104 



Tin Reconnaissance of the Kanuti 
and Hodzana Rivers Uplands, 
Central Alaska 

By James C. Barker and Jeffrey Y. Foley 




UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 



T 



Ntf 5 " 



As the Nation's principal conservation agency, the Department of the Interior has 7 / I 
responsibility for most of our nationally owned public lands and natural resources. This ■ ^ 
includes fostering the wisest use of our land and water resources, protecting our fish and , p 
wildlife, preserving the environment and cultural values of our national parks and / '- 
historical places, and providing for the enjoyment of life through outdoor recreation. The 
Department assesses our energy and mineral resources and works to assure that their 
development is in the best interests of all our people. The Department also has a major 
responsibility for American Indian reservation communities and for people who live in 
island territories under U.S. administration. 



:V 



Library of Congress Cataloging-in-Publication Data 



Barker, James C. 

Tin reconnaissance of the Kanuti and Hodzana Rivers uplands, cen- 
tral Alaska. 

(Information circular ; 9104) 

Bibliography: p. 

Supt. of Docs, no.: I 28.27: 9104 

1. Tin ores -Alaska -Kanuti River Watershed. 2. Tin ores -Alaska -Hodzana River 
Watershed. 3. Prospecting-Alaska-Kanuti River Watershed. 4. Prospec- 
ting -Alaska -Hodzana River Watershed. I. Foley, Jeffrey Y. II. Title. II. Series: Infor- 
mation circular (United States. Bureau of Mines) ; 9104. 



TN295.U4 [TN271.T5] 



PREFACE 



This is one of a series of Bureau of Mines reports that present the findings of 
reconnaissance-type mineral assessments of certain lands in Alaska. These reports in- 
clude data developed by both industry and government studies. 

Assessing an area for its potential for buried mineral deposits is a difficult task 
because no two deposits are identical. Moreover, judgments prior to drilling, the 
ultimate test, frequently vary among evaluators and continue to change as a result of 
more detailed studies. 

Included in these reports are estimates of the relative favorability for discovering 
mineral deposits similar to those mined elsewhere. Favorability is estimated by evalua- 
tion of outcrops, and analyses of data, including mineralogy, geochemistry, and evalua- 
tion of rock-forming processes that have taken place. Related prospects and the environ- 
ment in which they occur are subjectively compared to mineral deposits and en- 
vironments in well-known mining districts. Recognition of a characteristic environment 
allows not only the delineation of a trend but also a rough estimate of the favorability of 
conditions in the trend for the formation of minable concentrations of mineral materials. 



CONTENTS 



Abstract 

Introduction 

Acknowledgments 

Study area 

Land status and ownership 

Location and access 

Physiography and climate 

Previous work 

General geology 

Placer investigations 

Sampling methods 

Sithylemenkat pluton area 

Northern Ray Mountains area . 
Investigation of granitic plutons . 

Sampling methods 



Sithylemenkat pluton 

Ray River pluton 

Hot Springs pluton 

Fort Hamlin Hills pluton 

Coal Creek pluton 

Major-oxide analyses 

Trace-element analyses 

Discussion and recommendations 

Tin placer development potential 

Lode tin development potential 

Conclusions 

References 

Appendix A. - Geochemical analyses of rock samples . 
Appendix B.- Sample identification key 



ILLUSTRATIONS 



1. Location of study area and granitic plutons in central Alaska 

2. Location of concentrated placer samples 

3. Detail of sample locations on east fork of Kanuti Kilolitna River 

4. Stream profile of east fork of Kanuti Kilolitna River 

5. Broad, alluvial outwash valley of east fork of Kanuti Kilolitna River 

6. Geologic map of Sithylemenkat pluton 

7. Two aerial views of a structural intersection where chlorite-rich tin-bearing greisen occurs 

8. Rock sample location map for Sithylemenkat and Ray River plutons 

9. Sample location map for Hot Springs pluton 

10. Sample location and geologic map of metazeunerite occurrence in Hot Springs pluton 

11. Rock sample location map for Coal Creek and Fort Hamlin Hills plutons 

12. Comparison of Kanuti and Hodzana Rivers uplands plutons with Australian "tin-mineralizing granites" . 

13. Areas of tin development potential suggested for further placer investigations 



TABLES 

Tin analyses, weights, and volumes of placer concentrate samples 7 

Semiquantitative X-ray fluorescence spectrometry analyses of trace elements in nonmagnetic fraction of placer 

concentrates 8 

Major-oxide analyses and normative mineralogy of samples from plutons in Kanuti and Hodzana Rivers uplands 16 
Average concentration of trace elements in unmineralized rock samples from plutons in Kanuti and Hodzana 

Rivers uplands 17 

Geochemical analyses of rock samples collected in Ray River and Sithylemenkat pluton areas 21 

Geochemical analyses of rock samples collected in Hot Springs area 24 

Geochemical analyses of rock samples collected in Coal Creek and Fort Hamlin Hills pluton areas 26 



UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 



ft foot 

ft 2 square foot 

ft 3 cubic foot 

g gram 

in inch 

lb pound 

lb/yd 3 pound per cubic yard 



mi 2 
mm 


square mile 
millimeter 


pet 
ppm 
yd 3 


percent 

part per million 

cubic yard 


wt pet 


year 

weight percent 



TIN RECONNAISSANCE OF THE KANUTI AND HODZANA RIVERS UPLANDS, 
CENTRAL ALASKA 



By James C. Barker 1 and Jeffrey Y. Foley 2 



ABSTRACT 

The Bureau of Mines evaluated the tin development potential of the uplands between 
the Kanuti and Hodzana Rivers from 1978 through 1980. Chemical and petrologic data 
indicate that local granitic intrusions are generally similar to "tin granites" that contain 
tin deposits elsewhere. 

The tin mineral cassiterite (Sn0 2 ) was identified in chlorite-rich greisen from the 
Sithylemenkat pluton. Greisen zones are located near the intersections of high-angle, 
linear structural features, and samples contain up to 0.23 pet Sn. One bedrock exposure 
of greisen is 10 to 15 ft wide. 

Although some lode mineralization is present, the deeply eroded nature of the region 
suggests larger tin-bearing cupolas may have existed prior to erosion. Extensive stream 
gravel deposits have not been affected by glaciation, and potential exists for placer tin 
deposits. Especially favorable is a large semiclosed basin drained by the Kanuti Kilolitna 
River. Heavy mineral concentrates collected from surface alluvium in the Kanuti Kilolit- 
na River valley contained up to 51.2 pet Sn (0.02 to 0.4 lb/yd 3 Sn), up to 5 pet W, up to 0.4 
pet Cb(Nb), and up to 0.1 pet Ta. The concentration of heavy minerals is expected to in- 
crease with depth. Detailed mapping and extensive surface and subsurface sampling will 
be needed to quantify the mineral development potential of the lode and placer tin 
deposits in the uplands. 

■Supervisory physical scientist. 
Physical scientist. 
Alaska Field Operations Center, Bureau of Mines, Fairbanks, AK. 



INTRODUCTION 



The Bureau of Mines investigated tin and associated 
metals in the Kanuti and Hodzana Rivers uplands as part of 
a program to assess the mineral development potential of 
critical and strategic minerals in Alaska. (The area studied 
is shown in figure 1.) The initial investigations were 
authorized and partially funded by the Bureau of Land 
Management (BLM) to improve the mineral data base need- 
ed to develop management plans for the Trans-Alaska 
pipeline corridor and adjacent lands. Because the United 
States relies on imports of tin, and because tin is essential to 
industry, tin is of critical and strategic importance. 

Alaska has produced tin in the past and currently pro- 
duces small amounts from placer deposits. Geochemical tin 
anomalies in the Kanuti and Hodzana Rivers uplands were 
originally reported by the Alaska Department of Natural 
Resources (10) 3 and were later reported by the U.S. 
Geological Survey (USGS) (17) and the Bureau of Mines (2). 



Sources of the tin anomalies were not located during these 
studies, and further investigations were recommended. 
(More details of these and other previous studies are includ- 
ed in the "Previous Work" section.) 

The investigation reported here was initiated in 1978 
and included a literature search followed by geologic map- 
ping and sampling of surface exposures of both lode and 
placer tin occurrences. Field mapping was done during the 
field seasons of 1978 and 1979. Samples were collected for 
petrographic study and to determine chemical compositions 
of associated granitic plutons. Owing to logistical and per- 
sonnel constraints, the investigation was largely limited to 
the Sithylemenkat pluton area. Because no drilling or sub- 
surface sampling was done, the data presented in this 
report are not sufficient to completely assess the mineral 
development potential of the area. 



ACKNOWLEDGMENTS 



The Bureau of Land Management funded the early 
phases of this investigation. The U.S. Department of 
Energy, through the Bendix Field Engineering Corp., 
Grand Junction, CO, and the Los Alamos (NM) Scientific 
Laboratory, provided neutron activation, fluorometric, 
emission spectrographic, and X-ray fluorescence analyses of 
rock samples collected by the Bureau of Mines. Staff 



geochemists K. Stablien and W. Averett of Bendix super- 
vised the analytical procedures on behalf of the Bureau of 
Mines. K. Clautice, geologist, formerly with the Bureau of 
Mines, Fairbanks, AK, conducted field studies in 1978. M. 
McDermott, geologist, also formerly with the Bureau in 
Fairbanks, directed the 1979 field work. 



STUDY AREA 



LAND STATUS AND OWNERSHIP 



This report concerns lands in and adjacent to the 12- to 
24-mile-wide Trans-Alaska Pipeline corridor that parallels 
the Dalton Highway (fig. 1). The corridor is presently under 
Federal management according to Public Land Order 5150, 
but is being considered for transfer to State ownership. 
Lands east of the corridor are designated as part of the 
Yukon Flats National Wildlife Refuge. The northern portion 
of the Kanuti and Hodzana River uplands west of the cor- 
ridor is part of the Kanuti National Wildlife Refuge. To the 
south, the refuge is partially overlapped by unresolved 
Alaska Native selections. The land ownership pattern of the 
study area is likely to change in the near future as Native 
and State land claim entitlements are adjudicated. 



LOCATION AND ACCESS 

The uplands between the Kanuti River and the Hodzana 
River drainage systems are 100 to 140 miles northwest of 
Fairbanks. Except where accessible from the Dalton 



Highway (fig. 1), the area is best reached by helicopter or 
float plane. 

PHYSIOGRAPHY AND CLIMATE 

The uplands between the Hodzana and Kanuti Rivers 
are maturely eroded and are characterized by extensive 
alluvial gravel deposits in broad, terraced valleys with 
meandering streams that drain rounded hills. Outcrops are 
scarce. A generally treeless mat of vegetation covers all but 
the steepest terrain. The region is reported by Pewe (20) to 
be underlain by discontinuous permafrost. Alluvial deposits 
at these latitudes, however, are commonly frozen to depths 
of 100 to 400 ft. 

There is no evidence that glaciation has significantly af- 
fected the uplands area or has been a factor in the formation 
and preservation of placer deposits. Pleistocene ice ad- 
vances described by Hamilton (9) may have approached 
from the northwest, but the extent of glaciers or ice sheets 
is uncertain. They are not believed to have extended 
southeast of Sithylemenkat Lake. Some cirque and valley 
glaciation occurred in the Ray Mountains to the south of the 
study area, but studies by Yeend (24) indicate that the 
glaciers did not extend beyond the foothills. 

Climate in the study area is arctic continental. The ef- 
fective season for geologioc investigations extends from 
mid-May through late September. 







^ 



25 50 



Scale, miles 



I'Qhway 



I 



Y//\ P'utons investigated during this study 

I I | Bonanza pluton \7jA Coal Creek P |uton 

1 2 | Jim Riv er pluton \/ 7 /\ Fort Hamlin Hills pluton 

| 3 J Hodzana pluton J/p/J R ay River pluton 

I 4 | Kanuti pluton YM sitn y |emenka1 P'uton 

[///I Hot Springs pluton | 10 | Ray Mountains batholith. 

FIGURE 1.— Location of study area and granitic plutons in central Alaska. 



PREVIOUS WORK 

In 1963, a Bureau of Mines field crew observed an oc- 
currence of topaz, lithium, and radioactive yttrofluorite a 
short distance south of the study area. These minerals are 
frequently associated with lode tin deposits. The first known 
mention of tin in the area was in an Alaska Department of 
Natural Resources report published in 1969, in which Her- 
reid (10) reported that 10 granite samples from the 
Sithylemenkat pluton contained a mean of 32 ppm Sn, which 
is several times the normal trace-element background of tin 
in granitic rocks. In a 1970 USGS report, Patton and Miller 
(1 7) reported anomalous tin values in stream sediment (up to 
300 ppm Sn) and in two geochemical rock samples (20 and 
70 ppm Sn) from the Sithylemenkat pluton area; they 
recommended further investigation for lode and placer tin 
deposits. In 1973, the USGS released reconnaissance-scale 
(1:250,000) geologic maps and results of geochemical sam- 
pling in the Bettles and Southern Wiseman Quadrangles by 
Patton and Miller (18-19). Also in 1973, the USGS published 
the results of an aeromagnetic survey of the eastern Bettles 
Quadrangle (23). In 1978 and 1979, the Bureau collected 514 
heavy-mineral panned concentrates (2) and found anom- 
alous tin values in and southwest of the Sithylemenkat 



pluton area, near the westernmost part of the Hot Springs 
pluton, and northwest of the Fort Hamlin Hills pluton. 



GENERAL GEOLOGY 

The Kanuti and Hodzana Rivers uplands are underlain 
by crystalline rocks, including pelitic schists, quartzites, and 
phyllites of probable Paleozoic age (18). These rocks are in- 
truded by five principal composite plutons: the 
Sithylemenkat, Ray River, Fort Hamlin Hills, Coal Creek, 
and Hot Springs plutons. All are composed primarily of 
biotite granite and biotite quartz monzonite, with minor 
quartz diorite and rhyolite porphyry. 

A Cretaceous age is indicated for the plutons on the 
basis of available potassium-argon age determinations. 
Biotite from the Kanuti pluton immediately north of the 
study area (fig. 1) has been dated at 90.6 ±6 million yr (6). 
Biotite from the Hodzana pluton, located approximately 30 
miles north of the study area, has been dated at 101 ±5 
million yr (5). An age of 106 ± 3 million yr has been deter- 
mined for biotite from the Sithylemenkat pluton (18). 
Radiometric ages are not available for the younger rhyolite 
porphyry that locally intrudes the granitic plutons. 



PLACER INVESTIGATIONS 



SAMPLING METHODS 

Alluvial samples were shoveled from stream bars and 
cutbanks; cutbanks were preferentially sampled whenever 
possible. After they were measured and screened, the 
samples were sluiced with a regulated water flow and fur- 
ther reduced by panning. To compensate for the natural 
swell of loose, excavated material, the measured sample 
volumes were multipled by 0.80. 

Extensive tundra cover, flood-washed coarse sand, and 
a lack of cutbank gravel exposures are characteristic of the 
study area. In some places, the only gravel exposures were 
under standing or flowing water. Consequently, some of the 
samples were collected with a floating gasoline-powered 
suction dredge with a 5-in-diam intake. This sampling 
method was chosen because the equipment is portable and is 
capable of processing a large volume of gravel from below 
the water. Dredge sample volumes were estimated by 
measuring the resultant cone-shaped excavation. Suction 
dredge recovery efficiency can only be qualitatively as- 
sessed; an unknown amount of concentrate probably was 
lost owing to the turbulent flow of unsized material over the 
sluice. Where this method was used, the tin recovery results 
are considered to be conservative. 

The heavy-mineral samples were further prepared for 
analyses by heavy liquid and magnetic separation. 
Bromoform (2.85 specific gravity) was used to float the 
light-mineral fractions. The heavy fraction was then 
separated into magnetic and nonmagnetic fractions. Both 
the magnetic and nonmagnetic fractions were weighed, and 
the nonmagnetic fractions were analyzed for tin, tantalum, 
columbium (also called niobium), cerium, thorium, and 
tungsten by energy-dispersive X-ray fluorescence spec- 
trometry. 



SITHYLEMENKAT PLUTON AREA 

The initial reconnaissances by the Bureau in 1978 and 
1979 (2) indicated that the tin minerals are concentrated in 
alluvial gravels in the upper forks of the Kanuti Kiloitna 
River. Subsequent work has shown that placer samples 
(figs. 2-4) taken near the surface contain up to 0.4 lb/yd 3 Sn 
and lesser amounts of tantalum, columbium, tungsten, and 
rare-earth elements (tables 1 and 2). 

Based on the sampling results, the grade of placer 
gravels is expected to increase with depth. A higher grade 
at depth is indicated at sample location 5 (samples 5a-5b), 
where gravel from 0- to 2-ft depth contained 0.025 lb/yd 3 Sn, 
whereas gravel from 2- to 3-ft depth contained 0.076 lb/yd 3 
Sn. A similar relationship was observed at sample location 
2. (See samples 2a-2b in table 1.) 

The heavy-mineral content of surface samples varied 
markedly among closely spaced samples. Differences ap- 
peared to be related to the degree of washing during 
periodic floods. Generally, samples collected from com- 
pacted silt and clay-bound gravel in cutbanks and stream 
beds contained more tin. Gravel bars composed of fine, very 
loose, flood-deposited gravel with little silt and clay binder 
typically contained less heavy-mineral material. For exam- 
ple, at sample location 16, loose gravel on the right limit of 
the stream contained only 0.006 lb/yd 3 Sn, whereas silty 
gravel from the opposite cutbank contained 0.101 lb/yd 3 Sn. 
A sample of the intervening stream bed with more silt and 
clay contained 0.201 lb/yd 3 Sn. 

The principal tin-bearing drainage in the Sithylemenkat 
pluton area (fig. 2) is the east fork of the Kanuti Kilolitna 
River. This 10-mile-long tributary drains approximately 
one-third of the known areal extent of the Sithylemenkat 
pluton. Extensive alluvial deposits have accumulated along 




FIGURE 2.— Location of concentrated placer samples. 




FIGURE 3.— Detail of sample locations on east fork of Kanuti Kilolitna River. 




FIGURE 4.— Steam profile of east fork of Kanuti Kilolitna River. 



Table 1.— Tin analyses, weights, and volumes of placer concentrate samples 

(Samples are located by number In figures 2-4.) 



Sampling method and remarks 

Shoveled from active channel, concen- 
trated in 8- by 30-in portable sluicebox. 
Suction dredge sample from ac" 






Suction dredge sample from caisson be- 
tween 5- to 7-ft depth in gravel at same 
location as 2a. 

Suction dredge sample from active chan- 
nel along river. 

Suction dredge sample on active gravel 
bar with many medium-size boulders. 

Suction dredge sample from gravel bar 
along Kanuti Kilolitna River; cobbly gravel 
with boulders to 12-in diam; contains well- 
sorted gravel-silt fraction; cassiterite nug- 
gets noted. 

Shoveled from opposite side of gravel bar 
where 4a collected; screened and proc- 
essed through 12- by 36-in sluicebox. 

Shoveled from 5-ft-deep pit in dry stream 



deposited by river flooding. Sample pro- 
cessed in 12- by 36-in sluicebox. 
Suction dredge sample from depth of to 

2 ft in active channel of Kanuti Kilolitna 
River. 

Suction dredge sample from depth of 2 to 

3 ft in hole excavated for 5a. 
Shoveled from active channel and concen- 
trated in 8- by 30-in portable sluicebox. 



Shoveled from channel center; concen- 
trated by hand panning. 
Suction dredge sample from main channel; 

cobbles in creek to 14-in diam; most coarse 

posed granite sand. 
Shoveled from creek bank, approximately 

4 ft below tundra level; processed in 12- by 

36-in sluicebox. 
Located on left limit stream bank; sample 

shoveled from gravels immediately under 3 

ft of muck and tundra; processed in 12- by 

36-in sluicebox. 

nit alluvial 
in channel; 

concentrated in 12- by 36-in sluicebox. 



222.62 
73.11 



Do. 
Do. 

Shoveled from active flood-washed gravel 
bar near right limit bedrock bank; concen- 
trated in 12- by 36-in sluicebox. 

Shoveled from active gravel bar in main 
channel; concentrated In 12- by 36-in 
sluicebox. 

Suction dredge sample from streambed of 
the active channel. 

Shoveled from base of left limit cutbank, 
approximately 7 ft below tundra level; con- 
centrated In 12- by 36-in sluicebox; gravel 
contains higher silt fraction than observed 
elsewhere. 

Shoveled from upper alluvial bench approxi- 
mately 150 ft from stream; sample was dry, 
friable, and composed mostly of silt and 



See explanatory notes at end of table. 



Table 1.— Tin analyses, weights, and volumes of placer concentrate samples— Continued 







Volume, fi- 




Concentrate, g 


Sn, 


Sn in 
original 






Orig- 


Minus 




Nonmag- 


Mag- 


Sampling method and remarks 






5 in 


0.25 in 








vol, lb/yd 3 




18 


NA 


0.77 


0.46 


1.56 


0.01 


8.5 


'.010 


Shoveled from channel center; concen- 
trated by hand panning. 


19 




.93 


.46 
















.62 


.46 


9.33 




39.4 


'.353 


Do. 


21 


NA 


.93 


.46 


17.13 


.81 


33.7 


'.369 


Do. 


22a 


2 5.0 


3.64 


1.40 


47.60 


.06 


24.5 


.139 


Located on right limit of stream; sample 
shoveled and sluiced from bank approx- 
imately 4 ft below tundra level; gravel 
somewhat iron stained. 


22b 


! 59.5 


NA 


NA 


478.80 


10.40 


39.9 


.191 


Suction dredge sample from midchannel 

at 22a. 
Located on left limit, occasional boulders 


22c 


2 7.0 


4.71 


1.40 


69.57 


.10 


( 3 ) 


< 3 ) 


















up to 4-ft diam; samples shoveled and 
sluiced from bank approximately 6 ft below 


















23 


NA 


5.5 


NA 


102.31 


.29 


36.1 


'.399 


Shoveled from active channel; concen- 
trated in 8- by 30- in sluicebox. 


24 


NA 


3.04 




9.41 


.04 


41.9 


'.077 


Do. 


(4) 


NA 


5.5 


NA 


58.51 


7.48 


1 


'.001 


Sample shoveled from granitic terrane as a 
check on regional background Sn concen- 
trations; sluiced in 8- by 30-in sluicebox. 



y method did not permit accurate m 



>t owing to computer failure. 



n accompanying maps; sample from approximately 4.7 miles east of Dalton Highway in T 19 N, F 
NOTE.— Analyses by semiquantitative X-ray fluorescence spectrometry by the Bureau's Juneau (AK) laboratory. 



ement of in-place volume. 
/, section 13. 




'Not shown on accompanying maps; sample from approximately 4.7 miles east of Dalton Highway in T 19 N, R 



its lower course. Cassiterite, the only tin mineral identified 
in the area, is a major component in heavy-mineral fractions 
from the Kanuti Kilolitna River (based on identification by 
x-ray diffraction and petrographic methods, using a random 
suite of samples -samples 1, 6, 7, and 23-24, as listed in 
table 1). Cassiterite was found as nuggets ranging in size up 
to 0.75 in across and varying in color from mostly black to, 
less commonly, gray and brown. Larger nuggets that may 
have been present would have been lost during screening or 
sluicing of the sampled material. However, the cassiterite 
grains generally did not exceed the size of course sand. Nug- 
get loss, if it occurred at all, probably was not significant. 
The concentrated heavy-mineral samples also common- 
ly contained fragments of greisen with finely disseminated 
sulfide minerals and cassiterite. Although some pieces of 
greisen contained minor magnetite, the greisen fragments 
were found in the nonmagnetic fraction. Because of its 



lower specific gravity, most greisen material generally was 
not recovered in the heavy-mineral concentrates. Placer 
concentrates examined petrographically and by X-ray dif- 
fraction (samples 1, 6-7, and 23-24) also contained variable 
amounts of wolframite, pyrite, ilmenite, hematite, garnet, 
monazite(?), and lesser unidentified heavy minerals. The 
wolframite mineral in sample 23 was identified as ferberite, 
and traces of scheelite were observed by ultraviolet 
fluorescence in samples 7, 23, and 24. Generally, magnetite 
grains are sparse in the Sithylemenkat area (table 1) and 
comprise less than 0.5 wt pet of most concentrates. All of 
the concentrates in table 1 were visually examined; no gold 
and only trace amounts of scheelite were observed. 

Four gradient segments of the east fork of the Kanuti 
Kilolitna River were sampled. (See profile A-B-C in figure 
4.) The first segment, shown in figure 5, is the lower end of a 
broad alluvial outwash deposit. The outwash deposit is ap- 




proximately 0.25 mile wide and is bordered by terraced 
alluvial deposits. This lower segment contains the largest 
alluvial gravel deposits within the east fork valley and 
yielded some of the higher tin values (up to 0.404 lb/yd 3 Sn, 
from sample 7). The second gradient segment is a generally 
well-rounded valley with local bedrock constrictions in the 
lower portion and gravel terraces along the midsection to 
upper section. Samples from the lower portion (of the sec- 
ond segment) also contained significant tin values (samples 
13-14). The third segment is a more steeply inclined canyon 
with numerous boulders and little sediment accumulation. 
Although tin was found in samples (samples 15 and 
16a-16d), the lack of alluvial gravel deposits precludes 
potential for placer reserves. Lastly, the fourth, upper- 
valley segment is well-rounded and terraced, but is con- 
siderably narrower than the lower valley. Samples collected 
in this segment generally contained 0.1 to 0.4 lb/yd 3 Sn. The 
difference in tin content between the two upper forks (0.077 
lb/yd 3 Sn in sample 24 and 0.399 lb/yd 3 Sn in sample 23) is 
coincident with the occurrence of greisen veins within the 
area drained by the southern fork (sample 23). 

Two placer samples, 2a and 2b (fig. 2), were collected 
from a single location on the upper Ray River immediately 



downstream from the southeasterly margin of the 
Sithylemenkat pluton. Only minor concentrations of tin 
(0.008 to 0.015 lb/yd 3 Sn) were found; however, the only 
gravels available for sampling were well sorted and lacked a 
fine sediment fraction. Consequently, the relatively low tin 
values may or may not indicate a lack of significant placer 
tin at depth in the alluvium. 



NORTHERN RAY MOUNTAINS AREA 

The Ray Mountains, another possible source of tin 
located south of the study area, are underlain by a deeply 
eroded granitic batholith of the same name (figure 1, loca- 
tion 10). North-flowing streams, such as the south fork of 
the Kanuti Kilolitna River, have reworked and deposited 
alluvial and glaciofluvial granitic sediments beyond the 
foothills of the Ray Mountains and within the study area 
(fig. 1). Sample sites 3 and 4 (fig. 2) were selected because 
they are areas of slightly reduced stream gradient with a 
corresponding widening alluvial plain. To the south, the 
river is swift and turbulent and generally occupies a single 
channel, but braided sections occur locally where the gra- 
dient abruptly decreases. Beyond the foothills (north of sam- 
ple location 3 in figure 2), the gradient decreases, and the 
river becomes a meandering stream. 

Although the tin content in the gravels of the south fork 
of the Kanuti Kilolitna River was lower (not exceeding 0.08 
lb/yd 3 Sn) than that encountered on the river's east fork, the 
south fork gravels appeared to be considerably deeper and 
occupied a much wider river plain (varying from 0.25 to 1 
mile in width). Consequently, surface gravels are subject to 
reworking by migrating channels, and dilution occurs from 
other gravel sources. The heavy-mineral fraction would be 
expected to be more highly concentrated at some depth 
below the active streambed, and surface samples would only 
contain relatively low tin concentrations. For this reason, 
drilling or trenching is needed to further locate and assess 
cassiterite concentrations in the northern Ray Mountains 



INVESTIGATION OF GRANITIC PLUTONS 



SAMPLING METHODS 

Granitic plutons within the study area (fig. 1) were in- 
vestigated as potential hosts for tin deposits. Cassiterite- 
bearing float was found in the Sithylemenkat pluton area, 
and subsequent investigations identified several rubble ex- 
posures of tin greisen. The chemistry of the other plutons 
was compared with the chemistry of the Sithylemenkat 
pluton and well-known Australian tin granites to determine 
if the studied plutons are favorable for tin deposits. 

Rock samples were collected for petrographic examina- 
tion and major-oxide and trace-element analyses (Appendix 
A). Major-oxide samples were chipped from relatively 
unweathered, frost-riven boulders over areas of at least 
1,000 ft 2 . Samples collected for trace-element analyses con- 
sisted of random chips collected within a few feet of the 
sample station (unless otherwise noted in Appendix A). The 
descriptions of the samples listed in Appendix A were taken 
from field notes that were supplemented in some cases by 
thin-section examination. 



Sample analyses were provided by the U.S. Department 
of Energy (DOE) under an agreement with the Bureau of 
Mines. Analyses for beryllium and lithium were performed 
by emission spectrography. X-ray fluorescence was used for 
arsenic, silver, bismuth, cadmium, copper, columbium, 
nickel, lead, tin, tungsten, and zirconium analyses. Neutron 
activation with a short time delay before analysis was used 
for barium, chlorine, manganese, strontium, titanium, and 
vandadium analyses; neutron activation with a long time 
delay before analysis was used in analyses for gold, cerium, 
cobalt, rubidium, antimony, tantalum, thorium, and zinc. 
The procedures used and complete analytical results are 
presented in open file reports by DOE (2, 21). In these DOE 
reports, samples are identified by their field numbers; 
however, in this report, a simplified numbering system is 
used to identify the same samples. For this reason, a sample 
identification key (appendix B) is included to show the cor- 
respondence of the sample numbers used here with those 
used in the DOE reports (the field numbers). 



SITHYLEMENKAT PLUTON 

Geology 

The Sithylemenkat pluton is a 200-mi 2 composite 
batholith located west of the Dalton Highway (figs. 1 and 6). 
Geologic mapping confined to the northern half of the 
pluton identified four texturally different granite phases 
(fig. 6): porphyritic granite, granite porphyry, coarse- 
grained granite, and graphic granite. Age relations between 
the four phases are unclear because of a lack of outcrop. 

Mineralization 

Tin-bearing rocks were found in two areas in the 
Sithylemenkat pluton (MZ on figure 6), and mineralized 
float commonly occurs in the upper tributaries of the east 
fork of the Kanuti Kilolitna River. Chlorite-bearing and 
locally magnetite-bearing greisen are intermixed with 
aplite, frost-riven graphic granite (gg), and coarse-grained 
granite (eg) rubble. The north end of the western MZ area 
overlies an intersection of linear structural features (fig. 7) 
where the extent of greisen and otherwise altered rock 
could not be determined due to a lack of bedrock exposure. 
A north-trending greisen zone was traced for 1,200 ft along 
the southern end of the area. At one bedrock exposure, the 
zone was between 10 and 15 ft wide. 

Mineralized rock samples show variable effects of 
greisenization, with tourmaline and magnetite sometimes 
present. Fine-grained sericite- and quartz-rich veins and 
altered dikes contain abundant secondary chlorite, and 
locally contain up to several percent sulfide minerals, in- 
cluding pyrite, arsenopyrite, galena, and molybdenite. 
Greisen ruble is recognized in the field by its dark green to 
reddish-brown color, well-rounded weathered surface, and 
high specific gravity. 

In thin section, the greisen showed a relict porphyritic 
texture in which feldspar phenocrysts were replaced by a 
felty intergrowth of very fine-grained quartz and sericite. 
This material was further replaced by a felty aggregate of 
chlorite and clay minerals in more pervasively altered 
specimens. Anhedral bladed cassiterite grains, less than 1 
mm long and intimately intergrown with a felty aggregate 
of fine-grained chlorite, quartz, and white mica, were iden- 
tified petrographically in creek float of chloritic greisen col- 
lected downstream from sample location 71 (fig. 8). 

Greisen samples from the areas labeled MZ in figure 6 
contained from 25 to 2,300 ppm Sn (table A-l). Greisen 
samples from these areas also contained, up to in parts per 
million, 5,126 As, 326 Bi, 253 Cs, 1,808 Cu, 15,340 Mn, 
34,027 Pb, 1,156 Rb, 135 W, and 4,044 Zn (table A-l). 
Greisen from these areas ranges from light-colored to dark 
green. The highest tin concentrations were detected in the 
dark green chloritic greisen (sample 71d, figure 8 and table 
A-l). 

The extent of the tin-rich greisen at sample location 71 
was not determined, but it appeared to be concentrated in a 
300-ft-long, 100-ft-wide area along the east side of the 
south-striking ridge shown in figures 6 through 8. 



RAY RIVER PLUTON 
Geology 

The Ray River pluton is a poorly exposed intrusive body 
that occupies a 35-mi 2 area west of the Dalton Highway (fig. 



1). It is composed mainly of fine- to medium-grained 
equigranular granite and quartz monzonite, with subor- 
dinate amounts of nonequigranular to porphyritic granite. 
These rocks are composed of 30 to 50 pet orthoclase, 20 to 
40 pet oligoclase, 20 to 25 pet quartz, and less than 5 pet 
biotite. Muscovite and tourmaline were also observed in 
rocks from the center of the area, and feldspar is commonly 
altered to sericite and clay minerals. Aeromagnetic data (23) 
indicate that the Sithylemenkat and Ray River plutons may 
be connected at shallow depths. 



Mineralization 

No tin mineralization was observed in the Ray River 
pluton, and geochemical rock samples were not anomalous. 
Rock sample locations are shown in figure 8, and sample 
analyses and descriptions are presented in table A-l. 



HOT SPRINGS PLUTON 
Geology 

The Hot Springs pluton (fig. 1) is a 100-mi 2 east- 
trending granitic complex composed mostly of coarse- 
grained porphyritic and seriate biotite granite and biotite 
quartz monzonite with minor hornblende. The pluton is 
locally intruded by younger dikes and stocks of rhyolite por- 
phyry. 

In thin section, textures in the granitic rocks of the Hot 
Springs pluton vary from hypidomorphic to granular. 
Graphic and micrographic intergrowths among quartz and 
feldspar grains are common in the groundmass of these 
granites. Perthitic orthoclase, albite-twinned plagioclase, 
and biotite phenocrysts are set in a groundmass of anhedral 
quartz and two feldspars, with interstitial and euhedral 
biotite. Biotite phenocrysts sometimes contain metamict zir- 
con inclusions. Accessory minerals include tourmaline, zir- 
con, apatitie, magnetite, and pyrite. 

Dikes and stocks in the Hot Springs pluton area are 
composed of porphyritic rhyolite and granular, leucocratic 
granite. These rocks are variably altered and range in color 
from bleached white to iron-stained red. 



Mineralization 

Above-average concentrations of lithium, copper, 
arsenic, tin, antimony, lead, and uranium were detected in 
samples of altered rhyolite porphyry, biotite granite, and 
leucocratic granite that occur as rubble on a narrow, steep- 
sided ridge in the Hot Springs pluton. Metazeunerite 
[Cu(U0 2 )2(As0 4 ) 2 -8H 2 0] was identified by X-ray diffraction 
of sample 149, a gray-green-weathering, altered rhyolite 
porphyry that contained over 1,000 ppm U, 341 ppm Cu, 
2,616 ppm Pb, and 218 ppm Sn. Similar pieces of mineral- 
ized float were sparsely distributed along the ridge. The ex- 
tent of the mineralization is masked by soil and talus, but 
may account for tin anomalies in panned concentrates of 
alluvial gravel found nearby (2). Figures 9 and 10 show the 
sample locations and geology along the ridge and the loca- 
tions of other samples from the Hot Springs pluton. Results 
of the geochemical analyses are listed in table A-2. 




map of Sithylemenkat pluton. 




FIGURE 6--Geoli 




FIGURE 7.— Aerial views of structural intersection where a chlorite-rich tin-bearing greisen occurs (sample 
locations 72 and 73, as shown in figure 8), looking to the west (left) and north (right). 




FIGURE 8.— Rock sample location map for Sithylemenkat and Ray River plutons. 




FIGURE 9.— Sample location map for Hot Springs pluton. 




FIGURE 10.— Sample location and geologic map of metazeunerite occurrence in Hot Springs pluton. 







LEGEND 
• 180 Sample location and number 

Note : See appendix A for qeochemical analyse 



Contour interval 1000 ft 
FIGURE 11.— Rock sample location map for Coal Creek and Fort Hamlin Hills plutons. 



FORT HAMLIN HILLS PLUTON 
Geology 

The Fort Hamlin Hills pluton (fig. 1) underlies an 80-mi 2 
area between the Dalton Highway and the Yukon Flats. 
Most of the pluton is covered by unconsolidated surficial 
deposits. The Bureau's investigation was confined to the 
southern portion of the pluton, where the contact with horn- 
felsed Paleozoic schists and quartzites is exposed. The ex- 
amined area is composed mostly of medium- to coarse- 
grained, locally porphyritic biotite granite and quartz mon- 
zonite that are locally intruded by hydrothermally altered 
leucocratic, felsic dikes that contain accessory pyrite and 
tourmaline. 



Mineralization 



Sample 181 was collected from a tourmaline- and pyrite- 
bearing altered 5- to 8-ft-wide felsic dike that cuts the biotite 
granite. The dike was variably stained brick-red and green, 
and exposed for 50 ft along a north-trending strike. An 
altered zone extends into the granite for at least several 
feet. Secondary minerals in the dike and the biotite granite 
host rock include minor chlorite, sericite, tourmaline, 
hematite, and pyrite. Sample 181 contained 308 ppm Sn and 
1,102 ppm Rb, with traces of tantalum (29 ppm) and 
tungsten (16 ppm). The sample locations are shown in figure 
11, and the analytical results are listed in table A-3. 



Kanutl and Hodzana River uplands, 1 









(Samples 


are located by number in figures 8-11.; 










1 ". . . . 


46 


60 


110 


161b 170c 166 


137a 


150 


129 


184b 


MAJOR-OXIDE ANALYSES 



75.80 


76.20 


75.40 


77.60 


75.10 


71.90 


70.60 


78.00 


75.10 


74.80 




.20 


.26 


.12 




.38 


.45 




.35 


.15 


13.40 


12.40 


13.10 


12.60 


12.90 


14.20 


14.00 


12.30 


12.80 


13.00 


.65 


.86 


.26 


.24 


.33 


.73 


1.40 


.40 


1.10 


.78 


.83 


1.10 


1.40 


.35 


.57 


1.80 


1.70 


.13 


1.20 


1.00 


.03 


.04 


.04 


.02 


.02 


.05 


.05 





.04 


.02 


.15 


.22 


.31 


.04 


.09 


.56 


.81 


.07 


.37 


15 


.59 


.70 


.89 


.53 


.69 


1.70 


1.60 


.04 


.89 


.63 


3.20 


2.90 


2.80 


3.70 


3.40 


3.40 


3.20 


.38 


3.10 


3.00 


5.00 


5.30 


5.20 


3.90 


5.10 


5.20 


5.10 


4.90 


5.00 


5.30 


.02 


.02 


.02 


.02 


.02 


.10 


.09 


.02 


.08 


.02 


99.83 


99.97 


98.68 


99.12 


98.36 


100.02 


99.00 


96.35 


100.03 


98.85 



Orthoclase 
Albite 



NORMATIVE MINERALOGY 



Corundum . . . 
Hypersthene . 
Magnetite . . . 



34.45 


35.25 


34.50 


37.82 


32.58 


30.13 


32.09 


31.35 


23.55 


31.03 


29.31 


26.29 


25.66 


33.96 


31.44 



\7M 


26.78 


56.96 


35.34 


33.83 


30.73 


31.12 


31.31 


29.55 


32.34 


28.77 


29.67 


3.69 


26.23 


27.82 


7.78 


7.59 


.21 


3.89 


3.23 


.13 


.59 


7.44 


.86 


1.33 


3.56 


2.49 


.21 


1.71 


.68 


1.06 


.92 


.00 


1.59 


.54 


.72 


.65 


.10 


.66 


.22 


.23 


.19 





.19 






k technique by Skyline Laboratories, Wheatridge, CO. 



Coarse-grained porphyritic 



i nh micrographic 



110 Coarse-grained porphyr i . , 'lemenkat pluton. 

161b Coarse-grained biotite granite from Coal Creek pluton. 
170 Medium-grained biotite granite from Coal Creek pluton. 
166 Coarse-grained biotite granite from Coal Creek pluton. 
137a Porphyritic biotite granite with medium- to coarse-grained groundmass 
Rhyolite porp- i -! unngs pluton. 



e from Sithylemenkat pluton. 



129 Seriate to porphyritic biotite granite from H 
184b Coarse-grained biotite granite from Fort Hamlin 



COAL CREEK PLUTON 
Geology 

The 75-mi 2 Coal Creek pluton crops out east of the 
Dalton Highway and north of the Yukon Flats (fig. 11). This 
body is very similar in composition to the Sithylemenkat 
pluton. Porphyritic and seriate biotite granite and quartz 
monzonite are the most common rock types. Granular tex- 
tures are observed more rarely. Locally, veins and radial ag- 
gregates of tourmaline were observed. Siliceous fine- 
grained felsic rocks with tourmaline crystals up to 4 in long 
were commonly seen in float at the northeastern margin of 
the pluton. In thin section, the porphyritic rocks show 
micrographic and cataclastic textures. 

Mineralization 

No mineralization was observed during the Bureau's in- 
vestigation of the Coal Creek pluton. However, a previously 
reported stream-sediment sample collected from a gulch 
containing abundant vein quartz on the easternmost extent 
of the pluton contained 185 ppm U (1). Sample locations for 
the Coal Creek pluton are shown in figure 11, and the 
analytical results are listed in table A-3. 



MAJOR-OXIDE ANALYSES 

Major-oxide analyses on 10 chip samples (listed in table 
3 and located in figures 8-9 and 11) indicate that plutons in 
the Kanuti and Hodzana Rivers uplands are similar in com- 



position to tin granites found in New South Wales, 
Australia. Juniper and Kleeman concluded that "tin- 
mineralizing granites" can be characterized on the basis of 
their aluminum, calcium, iron, magnesium, potassium, 
silica, and sodium contents (U). For comparison, fields for 
tin-mineralizing granites in New South Wales, as determin- 
ed by Juniper and Kleeman (U), are shown in ternary 
diagrams in figure 12. The ternary diagrams are based on 
normalized compositions in the following systems: 

CaO + MgO + FeO : Si0 2 : Na 2 + K 2 + A1 2 3 (fig. 12A) 

Na + K : Fe : Mg (fig. 12B) 

K : NA : Ca (fig. 12Q 

Plots of samples from the Sithylemenkat, Coal Creek, Hot 
Springs, and Fort Hamlin plutons generally fell within the 
fields for tin-mineralizing granites. No samples were col- 
lected from the Ray River pluton for major-oxide analyses. 
A sample of rhyolite porphyry intrudes the plots near the 
tin-mineralizing fields in figures 12A and 12B, but is well 
outside the tin-mineralizing field in figure 12C. Samples 
from the Sithylemenkat, Coal Creek, and Fort Hamlin Hills 
plutons consistently plotted within, or very near, the fields 
for tin-mineralizing granites. 

TRACE-ELEMENT ANALYSES 

Trace-element analyses on 146 rock samples from 
plutons in the Kanuti and Hodzana Rivers uplands (appen- 



dix A) indicate that the plutons are chemically similar to tin 
granites elsewhere in the world. All are enriched in lithium, 
copper, zinc, arsenic, rubidium, tin, cesium, lead, tungsten, 
bismuth, and thorium. Locally elevated levels of columbium 
and tantalum were also detected. Only the Ray River pluton 
samples were enriched in beryllium, but all were depleted in 
barium. All but the Coal Creek pluton samples were 
depleted in manganese, and all but the Fort Hamlin Hills 
samples were depleted in zirconium. These enrichment- 
depletion findings, as compared to average granites, are 



common among tin granites described by various authors 
(3-4, 7-8, 11-13, 16, 22). 

Analyses of unaltered, nonmineralized samples from the 
plutons are summarized and compared to those of average 
granites in table 4. Mineralized or altered samples (which 
are not included in table 4). are noted in appendix A (foot- 
note 2 in each of the appendix tables). In table 4, the 
elements are presented in order of increasing atomic 
number, and the number of analyses (n) for each element 
varies due to matrix interferences during analysis. 





Coal Creek pli 



FIGURE 12.— Comparison of Kanuti and Hodzana Rivers uplands plutons with Australian 
mineralizing granites." 



Sithylemenkat 



Fort Hamlin Hill! 



66.36 
24.75 
271.34 
143.77 

10.04 
14.09 
261.48 



22.58 146 



'Analyses by Los Alamos (NM) Scientific Laboratories. 



DISCUSSION AND RECOMMENDATIONS 



TIN PLACER DEVELOPMENT POTENTIAL 

The data in tables 1 and 2 indicate that placer tin, 
tungsten, tantalum, and columbium minerals occur in 
deposits of unknown grade at several localities in the Kanuti 
Kilolitna River drainage. Sampling was limited to shallow 
pits. No samples were taken from near bedrock; therefore, 
the grade and extent of the underlying gravels could not be 
assessed. However, it is likely that the amount of concen- 
trate present per cubic yard of gravel increases with depth, 
particularly in the coarse granitic sands and gravels. 

Further work should include sampling of the subsurface 
gravels by backhoe trenching supplemented by drilling 
where necessary. It is suggested that the areas denoted on 
figure 13 (by the numbers 1 through 6) and listed below be 
sampled for placer concentrations of cassiterite and 
associated economic minerals. 

1. The westerly flowing streams, both north and south 
of the Kanuti Kilotina east fork valley, may contain relative- 
ly small but possibly high-grade stream placers. These 
streams drain areas where tin occurrences were found. 

2. The semiclosed basin drained by the south fork of the 
Kanuti Kilolitna contains complex alluvial and glaciofluvial 
deposits derived from the Ray Mountains batholith further 
to the south. The tin content of five placer samples 
downstream from Kilo Hot Springs (samples locations 3-4, 
figure 2) and heavy-mineral panned concentrates (2) from 
other tributaries suggest that cassiterite concentrations are 
present. The placer samples collected from flood-plain 
gravels contained 0.02 to 0.08 lb/yd 4 Sn. Exploration should 
assess the extensive active and ancient alluvial channels 
leading into and within the basin. Placer tin deposits, if pre- 
sent, may be large, but are likely of lower grade than the 
smaller stream placers. 

3. Placer deposits may be present in the active alluvium 
and alluvial terraces of the main valley of the Kanuti Kilolit- 
na River for 3 to 4 miles downstream of the basin mentioned 
above. Two placer samples collected from flood-plain 
gravels contained 0.03 to 0.08 lb/yd 3 Sn (sample locations 
5a-5b, figure 3). A sample from further upstream (location 
6, figure 3) contained approximately 0.02 lb/yd 3 Sn. 

4. Residual or eluvial placer deposits may occur in the 
immediate area of lode mineralization south of hill 3536 (fig. 
36). This area maybe more extensive than shown in figure 
13. 

5. Channel deposits in glaciofluvial outwash along the 
upper south fork of the Kanuti Kilolitna, which are derived 

Further field mapping and sampling is required to 
determine the significance of the tin anomalies in the 
western Hot Springs and Fort Hamlin Hills plutons. The 



northern poorly exposed portion of the Fort Hamlin Hills 
pluton is particularly recommended for further examination 
due to the presence of tin in panned concentrates, 
from the Ray Mountains, may contain significant placer tin 
deposits. The Ray Mountains batholith, south of the study 
area, is a deeply eroded granitic body; and although no lode 
tin mineralization is known, tin was previously found in pan- 
ned concentrate samples of alluvium derived from the 
batholith (2). 

6. West- and north-flowing streams, particularly the 
Ray River, which drains the Sithylemenkat pluton to the 
east, should be further evaluated for placer tin deposits, 
despite the relatively low values found in placer samples at 
location 2 (fig. 2). Panned concentrates from the upper Ray 
River contained anomalous tin (2). 

7. Areas of anomalous alluvial tin (2) in the north- 
western vicinity of the Fort Hamlin Hills and western Hot 
Springs plutons (not shown in figure 13 - see fgure 1) should 
be further evaluated for tin mineralization. Logistic con- 
straints prevented sampling in these areas during this in- 
vestigation. 



LODE TIN DEVELOPMENT POTENTIAL 

Major-oxide and trace-element analyses and tin occur- 
rences indicate that the plutons of the investigated area are 
chemically similar to other granitic intrusions that have 
given rise to tin mineralization. Tin mineralization in 
granites typified by their similar chemistries results from 
post magmatic processes involving the development of an 
alkali-rich volatile phase during crystallization (16). Tin 
greisen deposits are typically found in the upper, volatile- 
rich portions and cupolas of plutons. It is possible that such 
upper intrusive levels and associated tin deposits have been 
mostly or completely removed during subsequent erosion of 
the exposed plutons in the study area. The Sithylemenkat 
pluton, however, hosts several mineralized zones near the 
head of the east fork to the Kanuti Kilolitna River. This is 
evidence that at least some remaining deposits have escaped 
erosion. 

Trenching and further sampling near the mineralized 
zones in the Sithylemenkat pluton are needed to determine 
the nature and extent of mineralization. Additional detailed 
mapping is also needed to delineate the host phase of the tin 
occurrences. The distribution of placer tin indicates that the 
mineralized zones are, or were, more widespread than those 
found. Initially, magnetometer surveys may serve to better 
define the zones. 



CONCLUSIONS 



The east fork of the Kanuti Kilolitna River contains 
cassiterite with lesser amounts of tungsten, columbium, tan- 
talum, and rare-earth minerals in near-surface alluvial and 
bench gravels. These minerals were also found in the 
gravels of the south fork of the Kanuti Kilolitna near the 
foothills of the Ray Mountains. Placer samples collected 
from surface exposures commonly contained 0.02 to 0.14 
lb/yd 3 Sn. It is likely that the concentration of heavy 



minerals increases with depth. The sample results suggest 
that tin and associated elements may occur as placer 
deposits in these and other streams draining the granitic 
plutons in the Kanuti and Hodzana Rivers uplands. A large 
semibasinal area in the Kanuti Kilolitna drainage that con- 
tains ancient and present alluvial channels appears to be 
particularly favorable for large placer tin deposits. 

Analyses of rock samples showed that the granitic 




FIGURE 13.— Areas of tin reserve potential suggested for further placer investigations. 



plutons studied resemble granitic bodies elsewhere in the: 
world that are known to contain valuable deposits of tin and J 
associated metals. Mineralized zones in the Sithylemenkat; 
pluton were identified in rubble and indicate that at least 
some lode tin deposits exist. However, the deeply eroded 
nature of the region suggests that larger tin-bearing cupola 



zones, if originally present, may now be eroded away. 

Estimating the potential value of lode and placer tin 
deposits in the uplands between the Ranuti and Hodzana 
Rivers and adjacent areas will require extensive surface and 
subsurface exploration. 



REFERENCES 



1. Averett, W. R., and J. C. Barker. Report of Analyses from 
Mineral Resource Investigations in Central and Eastern Alaska. 
U.S. DOE Open File Rep. GJBX-178(81), 1981, 148 pp. 

2. Barker, J. C. Reconnaissance of Tin and Tungsten in Heavy 
Mineral Panned Concentrates Along the Trans-Alaska Pipeline 
Corridor, North of Livengood, Interior Alaska. BuMines OFR 
59-83, 1983, 24 pp. 

3. Beus, A. A. Geochemical Criteria for Assessment of the 
Mineral Potential of Igneous Rock Series During Reconnaissance 
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4. Boissavy-Vinau, M., and G. Roger. The Ti0 2 /Ta Ratio as an In- 
dicator of the Degree of Differentiation of Tin Granites. Miner. 
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5. Brosge, W. P., H. N. Reiser, and W. E. Yeend. Reconnaissance 
Geologic Map of the Beaver Quadrangle, Alaska. U.S. Geol. Surv. 
Misc. Field Stud. Map MF-525, 1973; 1 sheet; scale 1:250,000. 

6. Clautice, K. H. Geological Sampling and Magnetic Surveys of a 
Tungsten Occurrence, Bonanza Creek Area, Hodzana Highlands, 
Alaska. BuMines OFR 80-83, 1983, 80 pp. 

7. Flinter, B. H. Tin in Acid Granitoids: A Search for a 
Geochemical Scheme of Mineral Exploration. Paper in Geochemical 
Exploration. Can. Inst. Min. and Metall., Spec. v. 11, 1971, pp. 

8. Flinter, B. H., W. R. Hesp, and D. Rigby. Selected 
Geochemical, Mineralogical and Petrological Features of 
Granitoids of the New England Complex, Australia, and Their 
Relation to Sn, W, Mo and Cu Mineralization. Econ. Geol., v. 67, 
1972, pp. 1241-1262. 

9. Hamilton, T. D. Glacial Geology of the Lower Alatna Valley, 
Brooks Range, Alaska. Geol. Soc. America, Spec. Paper 123, 1969, 
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10. Herreid, G. Geology and Geochemistry, Sithylemenkat Lake 
Area, Bettles Quadrangle, Alaska. AK Dep. Nat. Resour., Geol. 
Rep. 35, 1969, pp. 1-3. 

11. Hesp, W. R. Correlations Between the Tin Content of 
Granitic Rocks and Their Chemical and Mineralogical Composition. 
Paper in Geochemical Exploration. Can. Inst. Min. and Metall., 
Spec. V. 11, 1971, pp. 341-353. 



12. Hesp, W. R., and D. Rigby. Some Geochemical Aspects of Tin 
Mineralization in the Tasman Geosyncline. Miner. Deposita, v. 9, 
1974, pp. 49-60. 

13. Hine, R., I. S. Williams, B. W. Chappel, and J. R. White. Con- 
trasts Between I- and S-type Granitoids of the Kosciusko Batholith. 
J. Geol. Soc. Aust., v. 25, 1978, pp. 219-234. 

14. Juniper, D. N., and J. D. Kleeman. Geochemical Characteriza- 
tion of Some Tin Mineralizing Granites of New South Wales. J. 
Geochem. Explor., v. 11, 1978, pp. 321-333. 

15. Levinson, A. A. Introduction to Exploration Geochemistry. 
Applied Publishing Ltd. (Maywood, IL), 1973, pp. 43-44. 

16. Olade, M. A. Geochemical Characteristics of Tin-Bearing and 
Tin-Barren Granities of Northern Nigeria. Econ. Geol., v. 75, 1980, 
pp. 71-82. 

17. Patton, W. W., Jr., and T. P. Miller. Preliminary Geologic In- 
vestigations in the Kanuti River Region, Alaska. Ch. in Contribu- 
tions to Economic Geology, 1969. U.S. Geol. Surv. Bull. 1312-J, 
1970, pp. J1-J10. 

18. Bedrock Geologic Map of Bettles and the 

Southern Part of Wiseman Quadrangles, Alaska. U.S. Geol. Surv. 
Misc. Field Stud. Map MF-492, 1973; 1 sheet; scale 1:250,000. 

19 Analyses of Stream-Sediment Samples From the 

Bettles and the Southern Part of the Wiseman Quadrangles, 
Alaska. U.S. Geol. Surv. Open File Rep. 73-219, 1973, 52 pp. 

20. Pewe, T. L. Quaternary Geology of Alaska. U.S. Geol. Surv. 
Prof. Paper 835, 1975, 145 pp. 

21. Stablien, N. K. Report on the Mineral Resource Investiga- 
tions in Six Areas of Central and Northeastern Alaska. U.S. DOE 
Open File GJBX-33(80), 1980, 186 pp. 

22. Tauson, L. V., and V. D. Kozlov. Distribution Functions and 
Ratios of Trace-Element Concentrations as Estimates of the Ore- 
bearing Potential of Granites. London Symp., v. 37-44, 1973, pp. 
37-44. 

23. U. S. Geological Survey. Aeromagnetic Survey, Eastern Part 
Bettles Quadrangle. Open File Map 73-305, 1973. 

24. Yeend, W. E. Glaciation of the Ray Mountains, Central 
Alaska. Paper in Geologic Survey Research 1971, Chapter D. U.S. 
Geol. Surv. Prof. Paper 750-D, 1971, pp. D122-D126. 



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APPENDIX B.— SAMPLE IDENTIFICATION KEY 

(Sample numbers used in this report related to field numbers used in DOE open file reports (1, 21)) 



Sample 



Sample 



KA 10838 
RM11014 
RM11015 
RM 10073 
RM 10074 
RM 10066 
RM 10067 
RM 10068 
RM11013 
RM11012 

KA10839 
KA10837 
RM11011 
PB15145 
PB10403 
PB10405 
PB10406 
PB10404 
PB16230 
PB16228 

PB16224 
PB16216 
PB16214 
PB16215 
PB16221 
PB16211 
PB16222 
PB16218 
PB16219 
PB16220 

PB15146 
PB10411 
PB10412 
PB10410 
KA10840 
KA10841 
PB12617 
PB12618 
PB15551 
PB15550 

PB11126 
PB15549 
PB15548 
PB12620 
PB11128 



PB11127 
PB10285 
PB10286 
PB10287 
PB10288 
PB10289 
PT11129 
PB10284 
PB11155 
PB11156 

KA 9696 
PB15878 
PB11157 
PB12657 
PB10192 
KA 9698 
PB10243 
PB12645 
PB12646 
PB12647 

PB12648 
PB12654 
PB12649 
PB15873 
PB15874 
PB15875 
PB10311 
PB10310 
PB10419 
PB12362 

PB15869 
PB15867 
PB15868 
PB10299 
PB10300 
PB10301 
PB16179 
PB12360 
PB16180 
PB12357 

PB12373 
PB16181 
PB12374 
PB12352 
PB12355 



71e PB12356 

71f PB16182 

72 PB12364 

73a PB12366 

73b PB16183 

74 PB12623 

75 PB10292 

76 PB10291 

77 PB10290 

78 PB12659 

79 PB12658 

80a PB10420 

80b PB10422 

81a PB16041 

81b PB16042 

82 PB10425 

83 PB10423 

84 PB10307 

85 PB10303 

86 PB10304 

87 PB15872 

88 PB15870 

89 PB12643 

90 PB11154 

91 PB11152 

92 PB12633 

93 PB12632 

94 PB12631 

95 PB12630 

96 PB12635 

97 PB12636 

98 PB10188 

99 PB10185 

100 PB10186 

101 PB10183 

102 PB10187 

103 PB12638 

104 PB11150 

105a .... PB12969 

105b .... PB12970 

106 PB12968 

107 PB11141 

108 PB11142 

109 PB11143 

110 PB15877 



PB12994 
PB12995 
PB12996 
PB12997 
PB11147 



PB15771 
PB15772 
PB15635 
PB15697 

PB12691 
PB12690 
PB12689 
PB12939 
PB12938 
PB12937 
PB15861 



PB15857 
PB15856 
PB15855 
PB15854 
PB15853 
PB16047 
PB16046 
PB16156 
PB16157 
PB12934 

PB12935 

PB12936 

PB236 

PB249 

PB12697 

PB12696 

PB12693 



PB 15595 
PB 15632 
PB 15695 
PB15631 
KA 9946 



KA11263 
KA11264 
PB15690 
PB15691 
PB15693 
PB15633 
PB15628 



PB15774 
PB15775 
PB15776 
KA 9961 
PB11131 
PB11132 
PB11133 
PB12925 
PB11134 
PB15799 



PB15802 
PB 15589 
PBv15587 
PBV15591 
PBV15590 
PBV15592 

PBV15593 
PBv15576 
PBV15561 
PBv15562 
PBV15559 
PBv15556 
PBV15563 
PBV15555 
PBV15564 
PBv15565 

PBV15568 
PBv15521 
PBV15522 
PBV15567 
PBv15662 



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